Venereal disease study: This study is concerned with investigating the etiology, epidemiology and clinical aspects of non-gonococcal urethritis (NGU). A major etiologic agent for this syndrome has not been established. The agents to be investigated in this study include: chlamydia, mycoplasma trichomonas and bacterial flora. An attempt will be made to correlate the clinical and epidemiological data with the laboratory findings. The study is projected to evaluate 300 patients and 300 controls. Counterimmunoelectrophoresis (CIEP) study: CIEP is being evaluated regarding the feasibility of its use in detecting dengue virus antigen in mosquitoes as well as Angiostrongylus cantonensis antigen in the cerebrospinal fluid of rats.